The present invention is directed to a highly simplified and inexpensive unidirectional rotary drive mechanism suitable for use in connection with multi-part construction toys. The invention is particularly useful in connection with, but by no means limited to, construction toys sold under the trademark "K'NEX". Certain features of the K'NEX construction toy system are exemplified by U.S. Pat. No. 5,199,919, granted Apr. 6, 1993.
Unidirectional drive mechanisms are well known and thoroughly understood. The present invention is directed, not to the concept of unidirectional drives in the broad sense, but to a special design for such a mechanism enabling it to be inexpensively fabricated from molded plastic parts and easily assembled into a functioning unidirectional drive by a typical person utilizing the construction toy.
In one of its most basic form, the unidirectional drive of the invention comprises inner and outer drive elements arranged when one of the elements is rotated in a first direction to have driving engagement and, when that same driving element is rotated in the opposite direction, to be able to rotate freely without driving engagement with the other element. The inner driving element is generally circular and has outwardly projecting, angularly oriented driving teeth. The outer element, which surrounds the inner element, has inwardly projecting, angularly oriented driving teeth capable of driving engagement with the teeth of the inner element. The driving teeth are fixed in relation to the driving element on which they are formed, and at least one of the driving elements is freely displaceable in a direction radially of the rotational axis of the driving elements. When the elements are rotated in the non-driving direction, the displaceable driving element is bodily displaced to a position in which the respective driving teeth are free of effective engagement. However, when one of the elements is rotated in a driving direction, the displaceable element immediately is displaced radially, by gravity or otherwise, to a slightly eccentric position in which the respective driving teeth are fully engaged, and a positive driving effect is achieved.
In a preferred embodiment of the invention, both of the driving elements are mounted on a common construction rod, forming a shaft. One of the driving elements is mounted for free rotation on the rod while the other has driving engagement with the rod by means of a snap-on clip which is secured to the rod and as a loose rotational driving connection with the other driving element, which allows the latter to be displaced radially in the manner desired.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments of the invention and to the accompanying drawings.